Apparatus and method for measuring displacement

ABSTRACT

Apparatus for measuring displacement that measures the displacement (the irregularities) of the surface of a measuring object precisely and at high speed is provided. The apparatus for measuring displacement scans light radiated toward the surface of the measuring object and measures the amount of displacement of the surface of the measuring object without contact based upon the position of an image formation point formed on the light receiving plane of a light receiving element. Light receiving means is provided with a lens array composed of plural condenser lenses which converges measuring beams and an imaging lens for forming an image formation point on the light receiving plane by converged measuring beams. Reflected light from an irradiation point is converged by the lens array. The converged reflected light is imaged on the light receiving plane by the imaging lens.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to apparatus and method for measuringdisplacement for measuring the displacement amount of a surface of ameasuring object without contact by scanning an irradiation point formedby light radiated onto the surface of the measuring object at a fixedinterval utilizing triangulation by light. Particularly, the presentinvention relates to apparatus and method for measuring displacement forenhancing displacement detection precision and a measurement rate usinga lens array. The present invention also relates to apparatus and methodfor measuring displacement that enable precisely acquiring the amount ofdisplacement by correcting an error due to the dispersion of a positionand a direction in which a lens array is installed and the focal length.

In case the displacement (irregularities) in the height of a surface ofa measuring object is (are) measured using light, an apparatus formeasuring displacement depending upon triangulation is used. In theapparatus for measuring displacement, a laser beam is radiated on thesurface of a measuring object 52 from a projector 51 as shown in FIG. 20and an image K at an irradiation point P is imaged on the lightreceiving plane of a light receiving element 54 through an imaging lens53.

This light receiving element 54 outputs a signal corresponding to theamount of displacement in which an image formation point on the lightreceiving plane moves from the position of K to K′ or K″. The lightreceiving element 54 is arranged to tilt for the optical axis of theimaging lens 53 as shown in FIG. 20. The light receiving element 54enables imaging in any position on the light receiving plane.

In this apparatus for measuring displacement, the irradiation point Pmoves in the direction of the height because of irregularities(displacement) on the surface of the measuring object 52 to be anirradiation point P′ or P″. Hereby, an image formation point K on thelight receiving plane of the light receiving element 54 moves to theposition of an image formation point K′ or K″. A signal from the lightreceiving element 54 also changes according to the amount ofdisplacement of the image formation point K. The displacement in theheight of the surface of the measuring object can be detected based uponthe amount of the change of the signal.

The above mentioned apparatus for measuring displacement is providedwith a mechanism for relatively displacing the measuring object 52 tothe direction of the x-axis and the direction of the y-axis respectivelyorthogonal to the direction of the height. This mechanism is a low-speedmechanism normally driven by a motor and others. Therefore, when themeasurement in minute pitch of the whole surface of the measuring object52 is tried, it takes very long time.

Therefore, recently, the displacement of a measuring object 70 can bemeasured by only displacement in only the direction of the y-axis usingscanning-type apparatus for measuring displacement 60 shown in FIG. 21.FIG. 21 is a schematic perspective view showing the scanning-typeapparatus for measuring displacement 60.

A projecting system of the scanning-type apparatus for measuringdisplacement 60 is composed of a light source 61, a deflector 62 such asan oscillating mirror type and a convergent lens 63. Light radiated fromthe light source 61 is deflected in a range of fixed angles by thedeflector 62. The deflected radiated light goes on one plane parallelwith the optical axis of the convergent lens 63. The radiated light isincident on the surface 70 a of the measuring object 70 set on ameasuring table 71 at a predetermined angle of incidence. An irradiationpoint P formed by the radiated light is linearly scanned on both ways oron one way.

The radiated light is regularly reflected in the position of theirradiation point P on a light receiving system. An image of theirradiation point P is imagined on a light receiving plane 66 a of alight receiving element 66 via a first cylindrical lens 64 and a secondcylindrical lens 65. In this apparatus for measuring displacement 60, incase the reflectance of the surface 70 a of the measuring object is highas that of a mirror, most of light reflected at the irradiation point Pis incident on the light receiving system at the same angle as the angleof incidence based upon the irradiation point P.

However, in case the surface 70 a of the measuring object is rough, thereflectance is low. In this case, the conventional scanning-typeapparatus for measuring displacement 60 using the cylindrical lenses 64and 65 for the light receiving system has a problem that when reflectedlight from the irradiation point P is scattered and is imaged on thelight receiving plane 66 a, an image on the light receiving plane is 66a of the light receiving element 66 becomes dim and the precision ofmeasurement is remarkably deteriorated.

That is, the cylindrical lenses 64 and 65 basically show convergence inonly the peripheral direction of the cylindrical face of each lens andhave no convergence in other directions. Therefore, as shown in FIG.22A, scattered light diffuse in the circumference of the cylindricalface of the first cylindrical lens 64 out of measuring beams reflectedat the irradiation point P is converged by the first cylindrical lens 64and is incident on the second cylindrical lens 65. The light isdeflected by the second cylindrical lens 65 so that the light goes tothe center of the light receiving plane 66 a of the light receivingelement 66 and forms an image formation point K on the light receivingplane 66 a.

Also, as shown in FIG. 22B, scattered light diffuse in the axialdirection of the cylindrical face of the first cylindrical lens 64 outof menacing beams reflected at the irradiation point P is not convergedby the first cylindrical lens 64 at all and is incident on the secondcylindrical lens 65 in a state in which the light is diffuse. Therefore,an image formation point K on the light receiving plane 66 a of thelight receiving element 66 becomes a straight line extended in the widthdirection of the light receiving plane 66 a.

In addition, an image at the irradiation point P is converged by onlythe first cylindrical lens 64 the focal length of which is short.Therefore, an image K on the light receiving plane 66 a of the lightreceiving element 66 is in the shape of arm ellipse long sidewaysbecause of the aberration of the first cylindrical lens 64 as shown inFIG. 23. Therefore, the image K in the shape of the ellipse longsideways cannot be made circular by converging it by the firstcylindrical lens 64. Hereby, the variation of a signal output from thelight receiving element 66 increases. Therefore, displacement on themeasured surface cannot be measured at high precision.

Further, as shown in FIG. 24, the surface 70 a of a measuring object 70has irregularities and may have predetermined difference in a level 70b. In such a form, when light radiated from a projecting system isregularly reflected by a light receiving system, reflected light may beintercepted by this difference in a level 70 b. In this case,displacement in the vicinity of a part having difference in a level 70 bcannot be measured.

SUMMARY OF THE INVENTION

The invention is made to remove the above-mentioned defects and theobject is to provide apparatus for measuring displacement that measuresthe displacement (the irregularities) of the surface of a measuringobject precisely and at high speed.

To achieve the object, apparatus for measuring displacement according toa first aspect of the invention is based upon apparatus for measuringdisplacement that scans light radiated onto the surface of a measuringobject and measures the displacement amount of the surface of themeasuring object without contact based upon a position in which an imageformation point formed on the light receiving plane of a light receivingelement is detected. Further, the above-mentioned apparatus formeasuring displacement comprises projecting means that radiates thescanned radiated light on the surface of the measuring object to form anirradiation point and light receiving means having the light receivingelement that receives a measuring beam from the irradiation point on thelight receiving plane of the light receiving element and forms the imageformation point. The light receiving means is provided with a lens arrayand an imaging lens. The lens array is composed of plural condenserlenses having a uniform image formation characteristic around theoptical axis and provided along the scan direction of the radiated lightfor converging the measuring beams. The imaging lens has a uniform imageformation characteristic around its own optical axis for guiding theconverged measuring beams onto the light receiving plane and forms theimage formation point.

The light receiving element may be also provided in a position apart byits focal length from the imaging lens as in a second aspect.

According to the above-mentioned configuration, light radiated onto thesurface of the measuring object is scanned by the projecting means andis reflected on the side of the light receiving means. Measuring beamsfrom the irradiation point are the reflected light or the scatteredlight of radiated light at the irradiation point formed on the surfaceof the measuring object. The measuring beams are converged in adirection orthogonal to a scan direction by the lens array. Theconverged measuring beams are imaged on the light receiving plane of thelight receiving element by the imaging lens having a uniform imageformation characteristic around the optical axis.

Therefore, the measuring beams converged by the lens array can be imagedon the light receiving plane in a state in which aberration is small.Hereby, the displacement of the surface of the measuring object can beprecisely measured.

Further, as described in a third aspect, each optical axis of the pluralcondenser lenses is mutually parallel and the plural condenser lensescomposing the lens array are arranged in parallel in a line orthogonalto each optical axis in a position respectively apart by the focallength from the irradiation point.

It is known that the larger light receiving width parallel to adirection scanned by radiated light is, the slower the speed of responseof a light receiving element is. A light receiving element the lightreceiving width of the light receiving plane of which is small and thespeed of response of which is fast can be used by configuring smallplural condenser lenses so that they converge measuring beams from anirradiation point. Hereby, the speed of a scan is accelerated, theprocessing speed of the light receiving element for the output of asignal can be accelerated and measuring time can be reduced.

Desirably, as described in a fourth aspect, when positional relationshipamong the lens array, the imaging lens and the light receiving elementmeets 0<(f1/f2)·t<w, an optimum image formation characteristic isacquired. However, w means light receiving width parallel to thedirection of a scan on the light receiving plane, t means the width ofeach condenser lens parallel to the direction of a scan, f1 means thefocal length of each condenser lens and f2 means the focal length of theimaging lens.

The apparatus for measuring displacement may be also configured asdescribed in a fifth aspect so that the projecting means verticallyradiates the scanned radiated light on the surface of the measuringobject and forms an irradiation point and a pair of light receivingmeans are provided apart by equal distance from the irradiation point insymmetrical positions based upon an optical path plane in the directionof a scan of the radiated light.

According to the above-mentioned configuration, radiated lightvertically incident on the surface of the measuring 25 object is scannedby the projecting means and is scattered in all directions in case themeasuring object has a rough surface. A part of scattered measuringbeams is converged in a direction orthogonal to the direction of a scanby the lens array. The converged measuring beams are imaged on the lightreceiving plane of the light receiving element by the imaging lenshaving a uniform image formation characteristic around the optical axis.

Therefore, measuring beams converged by the lens array can be imaged onthe light receiving plane in a state in which aberration is small.Hereby, the displacement of the surface of the measuring object can beprecisely measured. Particularly, even if measuring beams on the side ofone light receiving means are intercepted by difference in a level onthe surface of the measuring object and the sufficient amount of beamsis not acquired, the displacement is measured by beams acquired by theother light receiving means and the precision of measurement can bemaintained.

The apparatus for measuring displacement according to the fifth aspectis characterized in that it is provided with displacement operationmeans that operates and outputs a signal telling the displacement of thesurface of the measuring object based upon a position of the imageformation point formed on each light receiving plane of a pair of lightreceiving elements as described in a sixth aspect.

The displacement operation means is characterized as concretelydescribed in a seventh aspect in that it is provided with two preaddersthat add a pair of electric signals acquired from symmetrical positionsbased upon the optical path plane of the scanned radiated light afterfour electric signals acquired according to an image formation positionon each light receiving plane of a pair of light receiving elements areconverted from current to voltage, an adder that adds each electricsignal acquired in the preadders, a subtracter that subtracts anelectric signal acquired in one of the preadders from an electric signalacquired in the other and a divider that divides the electric signalacquired in the subtracter by the electric signal acquired in the adder.

According to the above mentioned configuration, the displacementoperation means can measure the amount of displacement precisely byadding and subtracting after adding electric signals output from thelight receiving element beforehand even if the amount of received lightvaries, the configuration of the divider is simplified and the cost ofthe apparatus for measuring displacement can be reduced.

As described in an eighth aspect, the displacement operation means isprovided with an adder and a subtracter in every light receiving means.The adder adds a pair of electric signals after the electric signalsacquired in an image formation position on each light receiving plane ofthe light receiving element are respectively converted from current tovoltage. The subtracter subtracts one of the pair of electric signalsfrom the other respectively. The displacement operation means may bealso provided with an addition signal adder that adds addition signalsacquired each adder, a subtraction signal adder that adds subtractionsignals acquired from each subtracter and a divider that divides anelectric signal acquired in the subtraction signal adder by an electricsignal acquired in the addition signal adder.

According to the above-mentioned configuration, even if balance in thesensitivity and others of both light receiving means is not uniform, thegain control and others of an amplifier can be facilitated and thedisplacement measurement precision can be enhanced.

Further, as described in a ninth aspect, the above-mentioneddisplacement operation means is provided with an adder, a subtracter anda divider in every light receiving means. The adder adds a pair ofelectric signals after a pair of the electric signals acquired in animage formation position on the light receiving plane of the lightreceiving element are respectively converted from current to voltage.The subtracter subtracts one of the pair of electric signals from theother. The divider divides a subtraction signal acquired in thesubtracter by an addition signal acquired in the adder respectively. Thedisplacement operation means may be also provided with switching meansto which each displacement signal corresponding to a value divided ineach divider and a displacement signal corresponding to the averagevalue of the divided values are input and which outputs any displacementsignal, level determination means that determines whether each additionsignal meets a predetermined reference value or not and selecting meansthat selectively outputs a suitable one of each displacement signalinput to the switching means based upon the result of determination inthe level determination means.

According to the above-mentioned configuration, in the displacementoperation means, the signal-to-noise ratio can be made satisfactorywithout increasing a noise level by adding, subtracting and dividingevery light receiving means, determining whether each addition signalmeets a predetermined reference value or not and outputting a suitabledisplacement signal acquired by division based upon the result ofdetermination and the displacement measurement precision can beenhanced. Particularly, when the amount of received light is small,predetermined precision can be also acquired.

Apparatus for measuring displacement according to a tenth aspect isbased upon apparatus for measuring displacement that scans radiatedlight on the surface of a measuring object and measures the amount ofdisplacement of the surface of the measuring object based upon aposition in which an image formation point formed on the light receivingplane of a light receiving element is detected without contact. Further,the above-mentioned apparatus for measuring displacement comprisesprojecting means, light receiving means, displacement operation meansand processing means. The projecting means radiates the scanned radiatedlight on the surface of the measuring object to form an irradiationpoint. The light receiving means has the light receiving element thatreceives a measuring beam from the irradiation point on the lightreceiving plane of the light receiving element and forms the imageformation point. The light receiving means is provided with a lens arrayand an imaging lens. The lens array is composed of plural condenserlenses having a uniform image formation characteristic around theoptical axis and provided along the scan direction of the radiated lightfor converging the measuring beams. The imaging lens has a uniform imageformation characteristic around its own optical axis for guiding theconverged measuring beams onto the light receiving plane and forms theimage formation point. The displacement operation means operates andoutputs the amount of displacement of the surface of the measuringobject based upon an electric signal corresponding to the position ofthe image formation point and output from the light receiving element.The processing means respectively detects the deviation of an imageformation position caused because of the dispersion of image formationpositions by light passed in the lens array in plural locations in thedirection of a scan, corrects and outputs the amount of displacement ofthe surface of the measuring object based upon the detected deviation.

As described in an eleventh aspect, the above-mentioned processing meansis characterized in that it is provided with deviation detection meansthat detects the deviation of the image formation position using areference object, correction value storage means that stores deviationdetected by the deviation detection means as correction data anddisplacement correction means that corrects and outputs the amount ofdisplacement output from the displacement operation means based upon thecorrection data stored in the correction value storage means inmeasuring the amount of displacement of the surface of the measuringobject.

Further, as described in a twelfth aspect, the apparatus for measuringdisplacement according to the eleventh aspect is provided with scaninitiation detection means that outputs a scan initiation signal everytime the radiated light scans and counting means that counts the currentradiated light scan position based upon a scan initiation signal fromthe scan initiation detection means and is characterized in that thedeviation detection means correlates the detected deviation with thecurrent radiated light scan position output from the counting means andstores in the correction value storage means as correction data and thedisplacement correction means reads correction data corresponding to thecurrent radiated light scan position output from the counting means fromthe correction value storage means, corrects and outputs a signal forthe amount of displacement output from the displacement operation meansby the read correction data.

Apparatus for measuring displacement according to a thirteenth aspect isbased upon apparatus for measuring displacement that scans lightradiated onto the surface of a measuring object and measures the amountof displacement of the surface of the measuring object without contactbased upon the detected position of an image formation point formed onthe light receiving plane of a light receiving element. Theabove-mentioned apparatus for measuring displacement is provided withprojecting means, the light receiving means, scan initiation detectionmeans and processing means. The projecting means radiates the scannedradiated light on the surface of the measuring object to form anirradiation point. The light receiving means has the light receivingelement that receives a measuring beam from the irradiation point on thelight receiving plane of the light receiving element and forms the imageformation point. The light receiving means is provided with a lens arrayand an imaging lens. The lens array is composed of plural condenserlenses having a uniform image formation characteristic around theoptical axis and provided along the scan direction of the radiated lightfor converging the measuring beams. The imaging lens has a uniform imageformation characteristic around its own optical axis for guiding theconverged measuring beams onto the light receiving plane and forms theimage formation point. The scan initiation detection means detects thescan initiated point of radiated light on the surface of the measuringobject. The processing means corrects and outputs the amount ofdisplacement of the surface of the measuring object based upon thedeviation of the image formation position caused because of thedispersion of image formation positions by light passed in the lensarray. Further, the processing means is provided with a calibration modeand a measurement mode. In the calibration mode, the deviation of theimage formation position caused by the dispersion of image formationpositions by light passed in the lens array is respectively detected inplural locations in the scan direction using a reference object. In themeasurement mode, the amount of displacement of the measuring object isrespectively corrected and output based upon the detected deviation inthe plural locations in the scan direction.

Further, a method for measuring displacement according to a fourteenthaspect is based upon a method for measuring displacement for scanning anirradiation point formed by light radiated onto the surface of ameasuring object, converging light from the irradiation point by a lensarray which is composed of plural condenser lenses having a uniformimage formation characteristic around the optical axis and in which theplural condenser lenses are arranged in the scan direction of theradiated light, forming the image formation point on the light receivingplane of the light receiving element and measuring the amount ofdisplacement of the surface of the measuring object without contactbased upon the deviation of an image formation position caused becauseof the dispersion of the positions of image formation points on a lightreceiving plane, and is characterized in that the deviation of the imageformation positions on the light receiving plane of the light receivingelement of each point in the scan direction of the surface of themeasuring object is detected using a reference object beforehand and theamount of displacement at each point in the scan direction acquired inmeasuring the measuring object is corrected based upon the deviation.

Also, as described in a fifteenth aspect, the method for measuringdisplacement according to the fourteenth aspect is characterized in thatthe radiated light scan position is sequentially detected by countingtime from scan initiation time and is used for the detection of thedeviation and for correction.

According to the above-mentioned configuration, light that scans thesurface of a measuring object is imaged on the light receiving plane ofthe light receiving element via each condenser lens of the lens arrayand the amount of displacement in the scan direction can be acquired.

Deviation which each condenser lens has can be detected using areference object. Deviation detection means stores the deviation of eachpoint in the scan direction in correction value storage means ascorrection data.

Displacement correction means reads correction data corresponding to theposition of a scan from correction value storage means in measuring ameasuring object, corrects and outputs the measured amount ofdisplacement referring to the correction data.

Hereby, deviation caused because of the dispersion in fabrication of thelens array and the dispersion of installation states in the equipment issolved by electric processing and high-precision displacementmeasurement is enabled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view showing apparatus for measuringdisplacement according to the invention;

FIG. 2 is a side view showing the apparatus for measuring displacementaccording to the invention;

FIG. 3 is a block diagram showing displacement operation means of theapparatus for measuring displacement according to the invention;

FIGS. 4A to 4E are top views respectively showing an image formationpoint corresponding to the scan of an irradiation point in lightreceiving means in an embodiment of the invention;

FIGS. 5A and 5B are side views respectively showing an image formationpoint corresponding to the irradiation point in the light receivingmeans in the embodiment of the invention;

FIG. 6 is a schematic perspective view showing apparatus for measuringdisplacement equivalent to a second embodiment of the invention;

FIG. 7 is a side view showing the apparatus for measuring displacementequivalent to the second embodiment of the invention;

FIG. 8 is a block diagram showing displacement operation means of theapparatus for measuring displacement equivalent to the second embodimentof the invention;

FIG. 9 is a side view showing the operation of the apparatus formeasuring displacement equivalent to the second embodiment of theinvention;

FIG. 10 is a side view showing a state in which scattered light isintercepted in case there is difference in a level in the vicinity of anirradiation point on a measuring object;

FIG. 11 is a block diagram showing another displacement operation meansin the second embodiment of the invention;

FIG. 12 is a block diagram showing the other displacement operationmeans in the second embodiment of the invention;

FIG. 13 is a block diagram showing the electric configuration of theapparatus for measuring displacement;

FIG. 14 is a flowchart showing a calibration mode of the apparatus formeasuring displacement according to the invention;

FIG. 15 is a front view showing a state in the calibration mode in whichthe equipment is installed;

FIG. 16 is the side view;

FIG. 17 shows deviation detected in the calibration mode of theapparatus for measuring displacement according to the invention;

FIG. 18 is a flowchart showing a measurement mode of the measuringobject;

FIGS. 19A to 19C are explanatory drawings for explaining processing forsolving deviation caused in a lens array;

FIG. 20 is a schematic drawing showing conventional type apparatus formeasuring displacement;

FIG. 21 is a schematic perspective view showing conventionalscanning-type apparatus for measuring displacement;

FIGS. 22A and 22B show the operation of a light receiving system of theconventional scanning-type apparatus for measuring displacement;

FIG. 23 shows an image formation point imaged on the light receivingplane of the conventional type apparatus for measuring displacement; and

FIG. 24 is a side view showing a state in which scattered light isintercepted in case there is difference in a level in the vicinity of anirradiation point on a measuring object.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1 and 2, apparatus for measuring displacement 1 scansa surface 30 a of a measuring object with light radiated from projectingmeans 2 and its light receiving means 6 receives the reflected light.The measuring object 30 is set on a measuring table 31.

The projecting means 2 is composed of a light source 3 such as a laserdiode, a deflector 4 such as a rotating mirror type, an oscillatingmirror type and a polygon mirror type and a convergent lens 5 forconverging light outgoing from the deflector 4 on the surface of themeasuring object.

The deflector 4 is arranged in a position in which radiated light isincident on the surface 30 a of the measuring object from a diagonaldirection. The deflector 4 deflects radiated light incident from thelight source 3 and scans the radiated light in fixed width.

The convergent lens 5 is arranged on the optical path of light outgoingfrom the deflector 4 so that the longitudinal direction is matched withthe direction of a scan. The convergent lens 5 converges radiated lightscanned by the deflector 4 and makes the radiated light parallel to theoptical axis incident on the surface 30 a of the measuring object.

An irradiation point P is formed on the surface of the measuring objectby radiated light.

The light receiving means 6 is composed of a lens array 7, an imaginglens 8 having a uniform image formation characteristic around theoptical axis and a light receiving element 9. The light receiving means6 is arranged on the optical path of reflected light.

The lens array 7 is composed of plural (six in FIG. 1) condenser lenses7 a to 7 f lined in the scan direction. Each condenser lens 7 a to 7 fis made of synthetic resin or glass and composes the lens array 7. Adimension of width in a direction in which the condenser lenses 7 a to 7f are arranged is shorter than width in which radiated light scans. Thefocal length f1 (for example, 20 mm) of each condenser lens 7 a to 7 fis mutually equal and each optical axis is parallel. Each condenser lens7 a to 7 f has a uniform image formation characteristic around itsoptical axis. One surface orthogonal to the optical axis of eachcondenser lens 7 a to 7 f is formed so that the surface is spherical.

The imaging lens 8 has a diameter larger than the dimension (forexample, 35 mm) of the width of a scan of reflected light. The imaginglens 8 is arranged so that the optical axis and the optical path ofreflected light are coincident. The plane of incidence of the imaginglens 8 is opposite to each condenser lens 7 a to 7 f and the outgoingplane is opposite to the light receiving plane. The imaging lens 8uniformly converges reflected light incident on the plane of incidencearound the optical axis and images the surface of the measuring objectat one point on the light receiving plane 9 a of the light receivingelement 9. The plane of incidence of the imaging lens 8 may be alsospherical or aspherical. The place of incidence may be also cut in ashape having only a part corresponding to a range on which reflectedlight is incident.

The light receiving element 9 is provided with the rectangular lightreceiving plane 9 a. The center of the light receiving plane 9 aintersects the optical axis of the imaging lens 8. The light receivingelement 9 is arranged in a position apart by the focal length f2 fromthe imaging lens 8. Light receiving width w parallel to the scandirection of the light receiving plane 9 a is set so that the lightreceiving width is larger than a value acquired by multiplying the widtht of each condenser lens 7 a to 7 f parallel to the scan direction bythe ratio (the magnification) f2/f1 of the focal length f1 of eachcondenser lens 7 a to 7 f and the focal length f2 of the imaging lens 8.For example, when the width in the scan direction of each condenser lens7 a to 7 f is 6 mm and the magnification f2/f1 is 4, the light receivingwidth w in the scan direction of the light receiving plane 9 a is largerthan 24 mm.

An image (an image formation point K) imaged on the light receivingplane 9 a moves in a direction orthogonal to the scan direction(hereinafter called the direction of displacement) by the displacementof the surface 30 a of the measuring object. The direction ofdisplacement has a predetermined gradient shown in FIG. 2 in ahorizontal direction to correspond to the movement of an image formationposition in the direction of the optical axis of the imaging lens 8according to the displacement of the surface 30 a of the measuringobject.

An electrode is provided at both ends in the direction of displacementof the light receiving element 9 to output a pair of electric signals Aand B corresponding to the position of the image formation point K. Whenthe surface 30 a of the measuring object approaches the lens array 7,the electric signal A relatively becomes large and the electric signal Bbecomes small. In the meantime, when the surface 30 a of the measuringobject separates from the lens array 7, the electric signal B relativelybecomes large and the electric signal A becomes small.

The electric signals A and B are output to displacement operation meansshown in FIG. 3. A pair of current/voltage converters I/V for convertingthe electric signals A and B from current to voltage is provided to thedisplacement operation means 10. The electric signals A and B convertedin each current/voltage converter I/V are respectively output to anadder 12 and a subtracter 13. In the adder 12, the electric signals Aand B are added and an addition signal is output. In the subtracter 13,the electric signal A or B is subtracted from the electric signal B or Aand a subtraction signal is output. The addition signal and thesubtraction signal are input to a divider 14, division is performedthere and a displacement signal D is output.

Next, referring to FIGS. 1 to 5A and 5B, the action of this embodimentwill be described. Light radiated from the light source 3 is deflectedby the deflector 4 and is scanned at a predetermined stroke. The scannedradiated light is incident on the convergent lens 5 to be parallel beamsand forms an irradiation point on the surface 30 a of the measuringobject. The radiated light is reflected or scattered every irradiationpoint P and reflected or scattered light (measuring beams) is/areoutgoing to the side of the light receiving means 6.

As shown in FIG. 4A, the irradiation point P is scanned and radiatedlight goes to a position opposite to the condenser lens 7 a at one endof the lens array 7. Light (measuring beams) reflected or scattered fromthe irradiation point is/are converged by the condenser lens 7 a to besubstantially parallel beams. The converged measuring beams are incidenton the imaging lens at an angle with the optical axis of the imaginglens 8.

The imaging lens 8 turns a measuring beam incident on the condenser lens7 a and images it on the side of one end of the light receiving plane 9a of the light receiving element 9 according to its image formationcharacteristic. As shown in FIG. 5A, light reflected or scattered fromthe irradiation point P is also converged by the condenser lenses 7 a to7 e to be substantially parallel when the light is viewed from the side.The light is imaged on the light receiving plane 9 a of the lightreceiving element 9 by the imaging lens 8.

Therefore, on the light receiving plane 9 a of the light receivingelement, a dot-shaped image Ka (an image formation point) is formed in aposition accurately corresponding to the height of the irradiation pointP. Electric signals A and B respectively corresponding to the positionare respectively output from the electrode. Measuring beams incident onthe other condenser lenses 7 b to 7 f from the irradiation point P arealso converged and are incident on the imaging lens 8. However, thesebeams are not imaged on the light receiving plane 9 a of the lightreceiving element 9.

As shown in FIG. 4B, the irradiation point P is displaced to a positionintersected with the optical axis of the condenser lens 7 a of the lensarray 7 by the scan of the irradiation point P. Light (measuring beams)reflected or scattered from this irradiation point P is/are convergedmainly by the condenser lens 7 a to be substantially parallel. Theconverged measuring beams are incident parallel to the optical axis ofthe imaging lens 8. Therefore, an image Ka of the irradiation point P isformed in a substantially central position in the direction of the lightreceiving width of the light receiving plane 9 a of the light receivingelement 9.

Further, as shown in FIG. 4C, the irradiation point P is displaced nearto the condenser lens 7 b adjacent to the optical axis in a rangeopposite to the condenser lens 7 a of the lens array 7 by the scan ofthe irradiation point P. Then, light (measuring beams) reflected orscattered from this irradiation point P is converged mainly by thecondenser lens 7 a. The measuring beams are incident on the imaging lensat an angle reverse to that in the case shown in FIG. 4A based upon theoptical axis of the imaging lens 8. Therefore, the imaging lens 8 formsa dot-shaped image Ka in a position on the side of the other end in thedirection of the light receiving width of the light receiving plane 9 aof the light receiving element 9.

As described above, when the irradiation point P is displaced in a rangeopposite to the condenser lens 7 a, the image Ka on the light receivingplane 9 a of the light receiving element 9 is displaced from the side ofone end of the light receiving width of the light receiving plane 9 a tothe side of the other end.

When the irradiation point P is displaced by d in the direction of theheight like P′ according to the scan of the irradiation point P as shownin FIG. 5B, an image on the light receiving plane 9 a of the lightreceiving element 9 is displaced like K′. Electric signals A and Bcorresponding to the position are output. The height of the irradiationpoint P′ from a reference level is detected based upon the electricsignals A and B and difference δ between the height and the height ofthe irradiation point P is also detected.

The irradiation point P is displaced to a position opposite to aboundary between the condenser lens 7 a and the condenser lens 7 baccording to the scan of the irradiation point P as shown in FIG. 4D.Measuring from the irradiation point P are converged by the adjacent twocondenser lenses 7 a and 7 b to be substantially parallel beams and areincident on the imaging lens 8. Therefore, image formation points Ka andKb are formed at both ends in the direction of the light receiving widthof the light receiving plane 9 a. However, the positions of these twoimage formation points Ka and Kb in the direction of displacement areequal. Therefore, an electric signal corresponding to the position inthe direction of displacement is output from the light receiving element9 as in a case that an image formation point is one.

When the irradiation point P is further scanned, it is displaced in arange opposite to the condenser lens 7 b as shown in FIG. 4E. Then,light (measuring beams) reflected or scattered from the irradiationpoint P is/are converted mainly by the condenser lens 7 b and is/areincident on the imaging lens 8 with the light (the measuring beams)having an angle with the optical axis. The imaging lens 8 forms adot-shaped image Kb in a position on the side of one end in thedirection of the light receiving width of the light receiving plane 9 aof the light receiving element 9.

Similarly, while the irradiation point P is scanned in the width in thedirection of a scan of the lens array 7 (in this case, 36 mm), the imageformation point K is displaced from one end of the light receiving widthof the light receiving plane 9 a to the other end every condenser lens 7a to 7 f. Simultaneously, according to the displacement of the surface30 a of the measuring object 30, the image formation point is displacedin the direction of displacement.

A pair of electric signals A and B accurately corresponding to thedisplacement in the height of the surface 30 a of the measuring object30 is output to the displacement operation means 10 from the lightreceiving element 9. The electric signals A and B are respectivelyconverted to voltage by the current/voltage converters I/V as shown inFIG. 3. The converted electric signals A and B are respectively outputto the adder 12 and the subtracter 13. After addition and subtraction,an addition signal is output from the adder 12, a subtraction signal isoutput from the subtracter 13, divider 14 divides the electric signal Aby the electric signal B and a displacement signal D is output from thedivider 14. The displacement of the surface 30 a of the measuring objectcan be measured based upon the displacement signal D.

The light receiving element 9 the light receiving width w of the lightreceiving plane 9 a of which is small can be used, compared with aconventional type method of converging measuring beams from theirradiation point to be substantially parallel by only the condenserlens having a uniform image formation characteristic around one opticalaxis the diameter of which is larger than a range in which radiatedlight scans and making them incident on the imaging lens. That is, it isknown that the larger the light receiving width w of this type of lightreceiving element 9 is, the slower the speed of response is. The lightreceiving element 9 the light receiving width w of the light receivingplane 9 a of which is small and the speed of response of which is fastcan be used by configuring so that measuring beams from the irradiationpoint P are converged by small plural condenser lenses 7 a to 7 f as inthis embodiment. Hereby, the speed of a scan is accelerated, theprocessing speed for outputting a signal of the light receiving element9 can be accelerated and measurement time can be reduced.

In this embodiment, the lens array 7 having five condenser lenses 7 a to7 e is used for the range of a scan of 36 mm by a beam, however, theinvention is not limited to this. If the condenser lenses 7 a to 7 e arefurther miniaturized (for example, the width is 2 mm), the lightreceiving width w of the light receiving plane 9 a of the lightreceiving element 9 can be further reduced and the processing speed foran electric signal output from the light receiving element 9 can befurther accelerated.

If the ratio f2/f1 of the focal length f1 of each condenser lens 7 a to7 e and the focal length f2 of the imaging lens 8 is reduced, the lengthin the direction of displacement of the light receiving element 9 can bealso reduced. In the meantime, when the focal length f2 of the imaginglens 8 is reduced, aberration is increased in the periphery of theimaging lens 8. When the focal length f1 is increased in a state thatthe width of each condenser lens 7 a to 7 e is fixed, the condenserlenses 7 a to 7 e become dark and the amount of received lightdecreases. Therefore, the outside diameter and the focal length of eachlens 7 and 8 may be determined according to a state of the surface ofthe measuring object 30 and precision required for measurement.

For the lens array 7 in this embodiment, the plural condenser lenses 7 ato 7 e are integrated by synthetic resin or glass. However pluralcondenser lenses 7 a to 7 e individually formed may be also bonded andintegrated and each condenser lens 7 a to 7 e may be also lined in astate without clearance without bonding.

In this embodiment, for the imaging lens 8, a lens one plane of which isspherical is used, however, it has only to be an imaging lens which canuniformly converge beams around its optical axis and a lens both planesof which are spherical or aspherical may be also used.

Second Embodiment

This embodiment is an example in which the projecting means 2 in thefirst embodiment is arranged in a position that light radiated from theprojecting means is vertically incident on the surface 30 a of ameasuring object and a pair of light receiving means 6 (6-1, 6-2) isprovided in positions symmetrical with the optical path plane of scannedradiated light so that measuring beams scattered at an irradiation pointP can be received as shown in FIGS. 6 and 7. The description of theconfiguration and functions respectively common to those in the firstembodiment is omitted below.

FIG. 8 is a block diagram showing electric configuration (displacementoperation means 15) that operates the displacement of a measuring object30 based upon the output of a pair of light receiving elements 9 (9-1,9-2).

This displacement operation means 15 is provided with a current-voltageconverter I/V, a preadder 11, an adder 12, a subtracter 13 and a divider14. The preadder 11 is configured by connecting a first preadder 11 aand a second preadder 11 b for converting an input electric signal tovoltage in parallel every light receiving element 9-1, 9-2. The adder 12adds an electric signal A from the preadder 11 a and an electric signalB from the preadder 11 b. The subtracter 13 subtracts the electricsignal B from the electric signal A. The divider 14 divides a signaloutput from the adder 12 or the subtracter 13 by a signal output fromthe subtracter 13 or the adder 12. The result of the division is outputas a displacement signal D.

Next referring to FIGS. 8 through 10, the action of this embodiment willbe described. Light radiated from a light source 3 is deflected by adeflector 4 and is scanned at a predetermined stroke. The scannedradiated light is converged via a convergent lens 5, is verticallyincident on the surface 30 a of the measuring object 30 on a measuringtable 31 and forms an irradiation point P on the surface 30 a of themeasuring object. Radiated light is scattered from the irradiation pointP because the surface 30 a of the measuring object is not a mirrorfinished surface. Scattered light (measuring beams) scattered at theirradiation point P is/are converged by both lens arrays 7 (7-1, 7-2),is/are converged around the optical axis by both imaging lenses 8 (8-1,8-2) and forms/form an image formation point K on both light receivingplanes 9 a.

The image formation point K formed on both light receiving planes 9 a isformed in positions symmetrical with the optical path plane of scannedradiated light. For example, as shown in FIG. 9, when the surface 30 aof the measuring object is displaced in the direction of the height andthe irradiation point goes to the position of P′, the image formationpoint both goes to the position of K′. When the surface 30 a of themeasuring object is displaced in the direction of the height and theirradiation point goes to the position of P″, the image formation pointboth goes to the position of K″.

A pair of electric signals (A1, B1) and (A2, B2) accuratelycorresponding to the displacement of the height of the surface 30 a ofthe measuring object 30 is respectively output from each light receivingelement 9 (9-1, 9-2). The displacement of each surface 30 a of themeasuring object can be measured based upon these electric signals.

As shown in a side view in FIG. 10, in case the irradiation point P islocated in the vicinity of part having difference in a level 30 b formedon the surface 30 a of the measuring object a measuring beam to bescattered in the direction of one light receiving element 9-1 (shown bya dotted line in FIG. 10) is intercepted by the side of a convexportion. In this case, no electric signal (A1, B1) corresponding to thedisplacement in the height of the surface 30 a of the measuring objectis output from one light receiving element 9-1 on which no image isimaged by interception.

However the image K of the irradiation point P is imaged on the otherlight receiving element 9-2 as described above. The electric signal (A2,B2) accurately corresponding to the displacement in the height of thesurface 30 a of the measuring object 30 is output. The displacement ofeach surface 30 a of the measuring object can be measured based upon theelectric signal.

The electric signals (A1, B1), (A2, B2) output as described above areprocessed as follows. As shown in FIG. 8, electric signals A1 and A2respectively converted to voltage are respectively input to the firstpreadder 11 a. Electric signals B1 and B2 respectively converted tovoltage are input to the second preadder 11 b.

In the first preadder 11 a, the electric signals A1 and A2 are added, inthe second preadder 11 b, the electric signals B1 and B2 are added andthey are respectively output to the adder 12 and the subtracter 13 aselectric signals A and B.

A value A+B added by the adder 12 and a value A−B subtracted by thesubtracter 13 are output to the divider 14. An expression (A−B)/(A+B) iscalculated in the divider 14, and is output as a displacement signal D.

As shown in FIG. 10, in case the irradiation point P is located in thevicinity of the part having difference in a level 30 b of the surface 30a of the measuring object and no image is imaged on one light receivingelement 9-1, no electric signals A1, B1 are output from the one lightreceiving element 9-1 for example. In this case, after only electricsignals A2 and B2 are converted to voltage, the preadder 11 outputs themas electric signals A and B. The output signals A and B are input to theadder 12 and the subtracter 13 and they respectively calculate A2+B2 andA2−B2. The divider 14 calculates an expression (A2−B2)/(A2+B2). Theresult of the division can be output a displacement signal D. Asdescribed above, as the divider 14 divides output acquired by addition(A2+B2) and by subtraction (A2−B2), the precise output of displacementcan be acquired without being influenced by the variation of the amountof received light.

As according to the displacement operation means 15 configured asdescribed above, the operation of displacement is executed afteraddition and subtraction are performed after output signals (electricsignals) from each light receiving element 9-1, 9-2 are addedbeforehand, plural disorders 14 are not required and the cost can bereduced.

The above-mentioned displacement operation means 15 executes theoperation of displacement after the means adds output signals (electricsignals) from each light receiving element 9-1, 9-2. However, as shownin FIG. 11, the operation of displacement may be also executed everyoutput signal from each light receiving element 9-1, 9-2. Concretely,the adder 12 and the subtracter 13 respectively included in thedisplacement operation means 15 are provided every light receiving means6-1, 6-2.

A subtraction signal sub1 output from a first subtracter 13 a and asubtraction signal sub2 output from a second subtracter 13 b are bothoutput to a subtraction signal adder 16. In the meantime, an additionsignal add1 output from a first adder 12 a and an addition signal add2output from a second adder 12 b are both output to an addition signaladder 17.

The subtraction signal adder 16 adds the subtraction signals sub1 andsub2 and outputs an electric signal sub showing the sum. The additionsignal adder 17 adds the addition signals add1 and add2 and outputs anelectric signal add showing the sum.

Both electric signals sub and add are input to a divider 14. Theelectric signal sub is divided by the electric signal add. The divider14 outputs a displacement signal D as a result of division.

The individual addition signals and individual subtraction signals arerespectively added according to displacement operation means 20 shown inFIG. 11 even if the sensitivity and others of both light receiving means6-1 and 6-2 are unbalanced. Therefore, the gain control and others of acurrent-voltage converter can be facilitated and displacementmeasurement precisian can be enhanced.

Further, the above-mentioned displacement operation means 15 executesthe operation of displacement after the means adds the correspondingoutput signals (electric signals) from each light receiving element 9-1,9-2, however, as shown in FIG. 11, the operation of displacement may bealso executed every output signal from each light receiving element 9-1,9-2. Concretely, the adder, the subtracter and the divider respectivelyshown in the displacement operation means 15 are provided every lightreceiving means 6-1, 6-2.

In displacement operation means 25, addition signals L1 (A1+B1) and L2(A2+B2) in each adder 12 are respectively input to level determinationmeans 21 and it is discriminated there whether the data L1 and L2respectively reach to a predetermined reference value or not. When it isdetermined that the data reaches to the reference value, the result ofdetermination is input to a decoder 22 which is selecting means.

In case the result of the determination tells that only the additionsignal L1 reaches to the reference value, a signal to output adisplacement signal D1 ((A1−B1)/(A1+B1)) on the side of one lightreceiving element 9-1 is output to switching means 23 and a switch S1 isselected. Hereby, the displacement signal D1 is output.

In the meantime, in case the result of the determination tells that onlythe addition signal L2 reaches to the reference value, a signal tooutput a displacement signal D2 ((A2−B2)/(A2+B2)) on the side of theother light receiving element 9-2 is output from the decoder 22 to theswitching means 23 and a switch S2 is selected. Hereby, the displacementsignal D2 is output.

In case the result of the determination tells that both the additionsignals L1 and L2 reach to the reference value, a signal to output theaverage value D3 of the displacement signals D1 and D2 of each lightreceiving element 9-1, 9-2 is output from the decoder 22 to theswitching means 23 and a switch S3 is selected. Hereby, an average valueD3 which is a result of equalizing processing by equalizing means 24 isoutput.

In case both the addition signals L1 and L2 do not reach to thereference value, the decoder 22 outputs an alarm signal telling thatmeasurement is disabled to an external device and the output ofdisplacement has a predetermined fixed value.

The displacement operation means 25 shown in FIG. 12 is provided withthe adder 12 and a subtracter 13 every light receiving element 9-1, 9-2to prevent noise from increasing, to acquire satisfactorysignal-to-noise ratio and to enhance displacement measurement precision.Particularly, even if light is incident on only one light receivingelement or sufficient quantity of light is not incident, predeterminedprecision can be acquired.

Third Embodiment

A third embodiment of the invention will be described below. The basicoptical system of apparatus for measuring displacement equivalent tothis embodiment may be the same as that in the first embodiment or inthe second embodiment. As shown in FIG. 1, for a measuring object 30loaded on a measuring table 31, there are a reference object 30A such asa block gage which is set when the equipment is in a calibration modeand the surface 30 a to be measured of which is a flat reference surfaceand a measuring object 30B set in a measurement mode.

FIG. 13 is a block diagram showing the electric configuration forcalibrating an error caused in a lens array 7 of the apparatus formeasuring displacement. Displacement operation means 14 shown in FIG. 13is the same as that 10, 15, 20 and 25 in the first embodiment and in thesecond embodiment. This displacement operation means 41 is operatedaccording to a clock pulse C supplied from clock generation means 40 andoutputs a displacement signal D showing the amount of displacement ofthe measuring object 30 based upon the output of a light receivingelement 9. For displacement operation processing in the displacementoperation means 41, after electric signals A and B output from bothelectrodes of the light receiving element 9 are converted to voltage,they are added or subtracted. A value acquired by dividing a subtractedsignal value by an added signal value is output to processing means 44as a displacement, signal D (D1, D2).

Scan initiation detection means 42 outputs a single scan initiationpulse S to counting means 43 every time the scan of radiated lightincident from a light source 3 is initiated.

The counting means 43 is composed of a counter, and a clock pulse C anda scan initiation pulse S are input. The counting means 43 outputs acount value as a count pulse C′ according to a clock pulse C every timea scan initiation pulse S is input.

The processing means 44 detects the deviation of an image formationposition caused because of the dispersion of image formation positionsby light passed in the lens array 7 in plural locations in the directionof a scan. The processing means corrects the amount of displacement ofthe surface of the measuring object based upon the detected deviationand outputs it. The processing means 44 includes deviation detectionmeans 45, displacement correction means 46 and correction value storagemeans 47.

The deviation detection means 45 is operated when the equipment is in acalibration mode and executes calibration processing. A signal showingthe displacement of the surface 30 a of the reference object 30A havinga smooth surface the contour of which is known beforehand (hereinaftercalled a displacement signal for correction) D1 and a count pulse C′from the counting means 43 are input to the displacement operation means41. The deviation detection means 45 stores the displacement ‘signal’for correction D1 in the correction value storage means 47 correlatingwith a count pulse C′. Hereby, the value of a displacement signal forcorrection D1 in each measuring position when the measuring object 30Bis scanned is stored corresponding to a count pulse.

The correction value storage means 47 is composed of ROM and RAM. Forexample, a displacement signal for calibration D1 is stored in a tableat an address corresponding to a count pulse C′ of erasable ROM. In ameasurement mode described later, reading can be accelerated bytransferring the contents stored in ROM to RAM beforehand.

The displacement correction means 46 is operated in a measurement modeand outputs a corrected displacement signal. A signal showing thedisplacement of the surface 30 a of the measuring object 30B(hereinafter called a displacement signal for measurement) D2 from thedisplacement operation means 41 and a count pulse C′ from the countingmeans 43 are input to the displacement correction means 46. Thedisplacement signal for calibration D1 output by the displacementoperation means 41 and this displacement signal for measurement D2 havethe same signal format and in this embodiment, for convenience, adifferent name is allocated every mode.

The displacement correction means 46 reads a displacement signal forcorrection D1 (data for correction E) stored at the correspondingaddress of the correction value storage means 47 (RAM) based upon acount pulse C′ from the counting means 43. The displacement correctionmeans 46 outputs a displacement signal corrected by correcting operationprocessing based upon a displacement signal for measurement D2 inputfrom the displacement operation means 41 and the data for correction E.This correcting operation processing means processing for subtractingthe data for correction E from the displacement signal for measurementD2.

Next, the operation of the equipment configured as described above willbe described every mode. FIG. 14 is a flowchart showing the contents ofprocessing in a calibration mode.

In the calibration mode, first, the apparatus for measuring displacement1 and the reference object 30A are set and adjusted by a correcting jig32 (ST1). FIG. 15 is a front view showing a state of the equipment inthe calibration mode and FIG. 16 is the side view.

The correcting jig 32 is provided with a butt plate 33 so that a datumclamp face T is horizontal. The butt plate 33 is adjusted so that thedatum clamp face T is parallel to the surface 31 a of the measuringtable 31. The reference object 30A is set on the measuring table 31. Atthis time, the apparatus for measuring displacement 1 is adjusted upwardor downward so that the surface 30 a of the reference object 30A can bemeasured.

Next, the apparatus for measuring displacement 1 is operated in thecalibration mode. Light radiated from the light source 3 is deflected bya deflector 4 so that the light is incident on the surface 30 a of thereference object 30A (ST2). At this time, the scan initiation, detectionmeans 42 outputs a scan initiation signal S to the counting means 43every time the deflection (scanning) of radiated light is started.

When an irradiation point P is linearly scanned on the surface 30 a ofthe reference object 30A, radiated light is regularly reflected towardlight receiving means 6 at the same angle as the angle of incidence andis incident on the lens array 7.

As the lens array 7 is the aggregate of plural condenser lenses 7 a to 7f having a uniform image formation characteristic around the opticalaxis, reflected light from each irradiation point P is converged inparallel, is further converged by an imaging lens 8 and is imaged on alight receiving plane 9 a (ST3).

As the surface 30 a of the reference object 30A is flat, an irradiationpoint P in any position on the surface 30 a is to be imaged in positiondetermined in the direction of displacement on the light receiving plane9 a. However, actually, displacement acquired from an image formationpoint K includes deviation shown in FIG. 17.

This deviation is caused because the focal length f1 is different everycondenser lens 7 a to 7 f of the lens array 7 and because of thedispersion of positions and directions in which condenser lenses in thelens array 7 are set in assembly. “t” is equivalent to time required forpassage in the width of each condenser lens 7 a to 7 f in scanning.

Electric signals A and B corresponding to this deviation are input fromelectrodes provided at both ends of the light receiving element 9 to thedisplacement operation means 41, displacement operation processing isexecuted and a displacement signal for calibration D1 is output to thedeviation detection means 45 (ST4).

In the meantime, when a scan initiation signal S and a clock pulse C areinput to the counting means 43, clock pulses are counted since the scaninitiation signal S is input (ST5). This count pulse C′ is output to thedeviation detection means 45.

The count pulse C′ is input to the deviation detection means 45 and iscorrelated with a displacement signal for calibration D1 every clockpulse C′1 to C′n. That is, a displacement signal for calibration D1 ofeach irradiation point P is stored in a table the address of whichcorresponds to a count value in the correction value storage means 47(ST6). In the correction value storage means 47, a displacement signalfor calibration D1 of each irradiation point P is stored at eachaddress. This displacement signal for calibration D1 has a valueequivalent to the above-mentioned deviation.

In scanning radiated light, time when radiated light passes in eachcondenser lens 7 a to 7 f of the lens array 7 is preset based upon clockpulses C since a scan initiation signal S is input.

Next, FIG. 18 is a flowchart showing the contents of processing in ameasurement mode. First, the measuring object 30B to be measured is seton the measuring table 31 LOT?). Next, measurement by the apparatus formeasuring displacement 1 is started. In both the above-mentionedcalibration mode and the measurement mode, the operation of an opticalsystem of the apparatus for measuring displacement 1 is similar and thedisplacement operation means 41 executes the similar displacementoperation processing.

That is, light is radiated from the light source 3, the radiated lightdeflected by the deflector 4 is incident on the surface 30 a of themeasuring object 30B set on the measuring table 31 and an irradiationpoint P is linearly scanned (ST8).

At this time, the scan initiation detection means 42 outputs a scaninitiation signal S to the counting means 43 every time a scan by lightradiated from the light source 3 is started.

An irradiation point P by the deflection of radiated light is scanned onthe surface 30 a of the measuring object 30B. This radiated light isreflected on the surface 30 a, is converged by the lens array 7, isfurther converged by the imaging lens 8 and is imaged on the lightreceiving plane of the light receiving element 9 (ST9). In measuring,displacement acquired from the position of an image formation point Kalso includes an error caused by the lens array 7 (deviation measured onthe surface 30 a of the reference object 30A).

FIGS. 19A to 19C show deviation caused due to the dispersion ofpositions where condenser lenses in the lens array are set and others.FIG. 19A shows the contour of the surface 30 a of the measuring object30B.

FIG. 19B shows deviation caused by each condenser lens 7 a to 7 f of thelens array 7. As shown in FIG. 19B, the positions of image formationpoints K in the direction of displacement on the light receiving plane 9a of the light receiving element 9 are different every condenser lens 7a to 7 f and displacement acquired from the position of an imageformation point K includes predetermined deviation.

Current signals A and B including this deviation are input from theelectrodes provided at both ends of the light receiving element 9 to thedisplacement operation means 41, operation processing is executed and adisplacement signal for measurement D2 is output to the deviationdetection means 45 (ST10)

In the meantime, when a scan initiation signal S and a clock pulse C areinput to the counting means 43, each clock pulse is counted since thescan initiation signal S is input (ST11).

This count pulse C is output to the deviation detection means 45.

The deviation detection means 45 acquires the position of the currentlyscanned irradiation point P based upon clock pulses C′1 to C′n includedin the count pulse C′ and correlates it with a displacement signal formeasurement D2 (ST12). In the correction value storage means 47, adisplacement signal for calibration D1 (correction data E showingdeviation) of each irradiation point P is stored at each address in theformat of a table.

The deviation detection means 45 reads correction data E stored at thesame count value (address) as the count value C′ of a displacementsignal for measurement D2 from the correction value storage means 47.The deviation detection means executes processing for subtracting thecorrection data E from the displacement signal for measurement D2(ST13).

FIG. 19C shows a displacement signal of the measuring object 30B afteroperation for correction. As shown in FIG. 19C, a displacement signal inwhich the deviation of the lens array 7 is solved can be output byoperating for correction using the correction data E.

As described above, the apparatus for measuring displacement accordingto the invention is useful for measuring the lit and bend of a lead IC,measuring the height of a solder ball of BGA, measuring the height ofcream solder printed on a printed wiring board and measuring the heightof a bump on a silicon wafer.

1. Apparatus for measuring displacement of a surface of a measuringobject comprising: projecting means having one convergent lens, saidprojecting means scanning radiated light on the surface of the measuringobject through the convergent lens to form an irradiation point on thesurface of the measuring object; and light receiving means including alight receiving element with a light receiving plane for receivingmeasuring beams reflected at the irradiation point to form an imageformation point on the light receiving plane, a lens array composed ofplural condenser lenses having a uniform image formation characteristicaround an optical axis thereof and arranged in a scanning direction ofthe radiated light for converging the measuring beams reflected at theirradiation point, and an imaging lens having a uniform image formationcharacteristic around an optical axis thereof for converging themeasuring beams passing through the lens array to form the imageformation point on the light receiving plane so that an amount of thedisplacement on the surface of the measuring object is obtained by usingtriangulation of light reflected on the surface of the measuring objectafter passing though said one convergent lens, passing through said lensarray and imaging lens, and forming the image formation point on thelight receiving plane, and a signal different according to a location ofthe image formation point on the light receiving plane.
 2. Apparatus formeasuring displacement according to claim 1, wherein the light receivingelement is provided in a position apart by a focal length from theimaging lens.
 3. Apparatus for measuring displacement according to claim1, wherein the plural condenser lenses have mutually parallel opticalaxes and are arranged in parallel in a position apart by a focal lengthfrom the irradiation point in a line orthogonal to each optical axis. 4.Apparatus for measuring displacement according to claim 1, wherein thelens array, the imaging lens and the light receiving element have arelationship expressed by an expression 0<(f2/f1)·t<w, wherein w is alight receiving width parallel with a direction of a scan of the lightreceiving plane, t is a width parallel with the scanning direction ofeach condenser lens, f1 is a focal length of the condenser lens and f2is a focal length of the imaging lens.
 5. Apparatus for measuringdisplacement according to claim 1, wherein the projecting means scansthe scanned radiated light perpendicular to the surface of the measuringobject to form the irradiation point; and the light receiving meansincludes a pair of light receiving units provided at an equal distancefrom the irradiation point in symmetrical positions from th an opticalpath plane of the radiated light.
 6. Apparatus for measuringdisplacement according to claim 5, further comprising displacementoperation means that operates and outputs a displacement signal of thesurface of the measuring object based upon a position of the imageformation point formed on each light receiving plane of the pair of thelight receiving units.
 7. Apparatus for measuring displacement accordingto claim 6, wherein the displacement operation means comprises twopreadders that respectively add a pair of electric signals acquired fromsymmetrical positions relative to the optical path plane of the radiatedlight after four electric signals corresponding to the position of imageformation point on the each light receiving plane of the pair of thelight receiving units are respectively converted from current tovoltage; an adder that adds each electric signal acquired in thepreadders; a subtracter that subtracts an electric signal acquired inone of the preadders from an electric signal acquired in the other ofthe preadders; and a divider that divides an electric signal acquired inthe subtracter by an electric signal acquired in the adder.
 8. Apparatusfor measuring displacement according to claim 6, wherein thedisplacement operation means comprises an adder and a subtracter foreach of the light receiving units, said adder adding a pair of electricsignals after the pair of the electric signals corresponding to theposition of the image formation point on the each light receiving planeof the light receiving units is respectively converted from current tovoltage, said subtracter subtracting one of the pair of the electricsignals from the other; an addition signal adder that adds additionsignals acquired from each adder; a subtraction signal adder that addssubtraction signals acquired from each subtracter; and a divider thatdivides an electric signal acquired in the subtraction signal adder byan electric signal acquired in the addition signal adder.
 9. Apparatusfor measuring displacement according to claim 6, wherein thedisplacement operation means comprises an adder, a subtracter and adivider for each of the light receiving units, said adder adding a pairof electric signals after the pair of the electric signals correspondingto the position of the image formation point on the each light receivingplane of the light receiving units is respectively converted fromcurrent to voltage, said subtracter subtracting one of the pair of theelectric signals from the other; and said divider dividing a subtractionsignal acquired in the subtracter by an addition signal acquired in theadder; switching means that receives each displacement signalcorresponding to a divided value divided in the each divider and adisplacement signal corresponding to an average value of the dividedvalues so as to switchably output one of the displacement signals; leveldetermination means that determines whether the each addition signalmeets a predetermined reference value or not; and selecting means thatselectively outputs a suitable one of the each displacement signal inputto the switching means by switching based upon a result of determinationin the level determination means.
 10. Apparatus for measuringdisplacement of a surface of a measuring object comprising: projectingmeans that radiates light for scanning the light on the surface of themeasuring object to form an irradiation point on the surface of themeasuring object; light receiving means including a light receivingelement with a light receiving plane for receiving measuring beams fromthe irradiation point thereon to form an image formation point on thelight receiving plane, a lens array composed of plural condenser lenseshaving a uniform image formation characteristic around an optical axisthereof and arranged in a scanning direction of the radiated light forconverging the measuring beams, and an imaging lens having a uniformimage formation characteristic around an optical axis thereof forconverging the measuring beams to form the image formation point on thelight receiving plane using triangulation of light; displacementoperation means that operates and outputs an amount of the displacementof the surface of the measuring object based upon a position of theimage formation point formed on the light receiving plane of the lightreceiving element; processing means that detects a deviation of theimage formation point caused because by dispersion of the imageformation point of light passed in the lens array in plural locations ina direction of a scan, corrects and outputs the amount of thedisplacement of the surface of the measuring object based upon thedetected deviation, said processing means including deviation detectionmeans for detecting the deviation of the image formation point using areference object, correction value storage means for storing thedeviation detected by the deviation detection means as correction data,and displacement correction means for correcting and outputting theamount of the displacement output from the displacement operation meansbased upon the correction data stored in the correction value storagemeans when the amount of the displacement of the surface of themeasuring object is measured; scan initiation detection means foroutputting a scan initiation signal whenever the radiated light isscanned; and counting means for counting a current position scanned bythe radiated light based upon the scan initiation signal from the scaninitiation detection means, wherein said deviation detection meanscorrelates the deviation with the current position scanned by theradiated light output from the counting means and stores in correctionvalue storage means as correction data, and said displacement correctionmeans reads the correction data corresponding to the current positionscanned by the radiated light output from the counting means from thecorrection value storage means and corrects the amount of thedisplacement output from the displacement operation means by thecorrection data.
 11. A method for measuring displacement, comprising:scanning light on a surface of a measuring object through one convergentlens to form an irradiation point on the surface of the measuringobject, converging the light from the irradiation point by a lens arraycomposed of plural condenser lenses having a uniform image formationcharacteristic around an optical axis thereof and arranged in a scanningdirection of the light, forming an image formation point on a lightreceiving plane of a light receiving element by an imaging lens,detecting a deviation of the image formation point on the lightreceiving plane of the light receiving element by using a referenceobject, correcting an amount of the displacement based upon thedeviation, and measuring the amount of the displacement of the surfaceof the measuring object using triangulation of light without contactbased upon the deviation of the image formation point on the lightreceiving plane.
 12. A method according to claim 11, further comprisingdetecting a scan position of the light by counting time since the scanis started for detecting the deviation and correcting the amount of thedisplacement.
 13. Apparatus for measuring displacement of a surface of ameasuring object, comprising: a light source for irradiating light, adeflector disposed between the light source and the measuring object fordeflecting the light from the light source to scan the light on thesurface of the measuring object at a first angle relative to thesurface, a convergent lens disposed between the light source and themeasuring object for converging the light from the deflector on thesurface of the measuring object with the first angle, a lens arrayformed of plural condenser lenses and arranged in a line for convergingthe light reflected from the surface of the measuring object at a secondangle relative to the surface different from the first angle, an imaginglens for converging the light from the lens array, and a light receivingelement for receiving the light from the imaging lens converged at animage formation point on a light receiving plane thereof so that anamount of the displacement of the surface of the measuring object isobtained based upon a position of the image formation point formed onthe light receiving plane using triangulation of light.